[RESOLVED] can dirty fuel fiter cause misfire?

[dsm1gawdfox]

my 90 gsx is misfireing while idleing and driving and wont rev past 4,000rpm and wont boost at all. The car is bone stock besides 3"catback exhaustand walbro 255 pump. I have checked all of my ignition components.(coil pack, power tr, plugs and wires) I have also checked my cas and fuel injectors and every other sensor on the vehicle and i can not figure these problems out. I started thinking maybe a dirty fuel filter. would that cause a misfire?


UPDATE:
The misfire problem was resolved, my ecu was bad i swapped it with 91-94 ecu but now it is followed by another issue. Now the car wont boost at all or rev past 4000rpm. Look below for the update posted by Assault 187.

 

[grail97]

is it constant and is it a hesitation or stumble or pop? need more info.. could be gap on plugs week ignition component or possibly a fuel filter... or maybe ev en a vaccum leak..

 

[crimsondragon]

It could if it manages to somehow bypass the sock filter at the pump and then the fuel filter in the engine bay.

 

[dsm1gawdfox]

Replaced plugs and gapped to .028
Checked mechanical timing and its spot on (checked by Assault187)
replaced MAF
Replaced coil pack
No CEL's
Boost leak test reveals tiny leak at throttle body shaft seals
Tested Power transistor per VFAQ
Tested CAS per VFAQ

I started the car and let it get up to temp then took it around the block, It hesitates, spudders and misfires all the way up to 4,000 rpm then wont go further past that rpm.

When the car is cold and I start it, It wants to die rite out within a few seconds.

 

[assault187]

Hmm...come to think of it, I may have a trick up my sleeve for tomorrow, Thats if its fuel related.

 

[dsm1gawdfox]

Hmm...come to think of it, I may have a trick up my sleeve for tomorrow, Thats if its fuel related.

i hope your sleeve trick works so i can start driving my car again.

 

[assault187]

Replaced plugs and gapped to .028
Checked mechanical timing and its spot on (checked by Assault187)
replaced MAF
Replaced coil pack
No CEL's
Boost leak test reveals tiny leak at throttle body shaft seals
Tested Power transistor per VFAQ
Tested CAS per VFAQ

I started the car and let it get up to temp then took it around the block, It hesitates, spudders and misfires all the way up to 4,000 rpm then wont go further past that rpm.

When the car is cold and I start it, It wants to die rite out within a few seconds.

Adding to the list ...

Swapped ECU (This took care of the idle and misfire problems)
Swapped coil pack
swapped power transistor
swapped resistor pack for injectors
swapped CAS
disconnected knock sensor to test for any differences
No shaft play on 14b and it rotates freely
Removed and inspected 255 fuel pump, filter looks good and no fuel leaks
Rewired fuel pump
tested TPS


problem persists...Can not drive or rev past 4,000 rpm, the rev is smooth untill that point though.... and no boost at all while driving


This is my brothers car by the way.... And im stumped of what this problem could be.



Andrew, change the thread title to "troubleshooting Rev/boost issue" or somthing similar so it will get more responses

 

[96mitsugsx]

Check your fuel pressure.

 

[dsm1gawdfox]

I'll check the fuel pressure tomorrow if I can find a pressure gauge and post back with my findings.

 

[crimsondragon]

You guys don't have an AFPR for that 255?

 

[dsm1gawdfox]

You guys don't have an AFPR for that 255?

No, I actually just picked up the car a few weeks ago...

 

[assault187]

Problem was resolved.

For the insane misfire
#1. Bad ecu (caps were leaking)
Fix= Replaced ECU with 91+ ecu, Wire up 91+ Power transistor, and swap 2 wires @ the ecu harness

For the limited rev (no higher then 4k rpm)
#2. A 91+ PT is needed when using 91+ ecu in 90.
Fix= pick up 91+ PT and harness, all the wires match up color for color except 2. Black/white is spliced into the 90 Coilpack harness's black/white and the white wire replaces the existing white wire @ the ecu harness pin 109

For the no boost situation
#3. Sealing ring (14b housing to manifold sealing ring) was distorted somehow and made its was into the ex. housing of the turbo restricting air flow (Still spun freely with no shaft play)...One of the oddest things I have ever seen!